1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to methods for disinfecting implanted devices and to modified devices which facilitate such disinfection methods.
Subcutaneously and transcutaneously implanted devices are utilized for a wide variety of purposes. Heart pacemakers have become commonplace. Transvascular catheters are used for a variety of purposes, including hemodialysis access, drug infusion, and the like. Of particular interest to the present invention, subcutaneously and transcutaneously implanted ports and catheters have been proposed for both drug infusion and hemodialysis access. All such implanted devices are subject to infection of surrounding tissue pockets. Subcutaneously implanted ports which are periodically accessed by needles and other percutaneously introduced devices are particularly subject to infections introduced by the access device.
Heretofore, infections of subcutaneously implanted devices have usually been treated by administering antibiotics to the patient after infection has become established. Most often, the implanted device must also be removed and replaced, subjecting the patient to additional trauma and leaving the patient without benefit of the device for the time it takes to clear the infection and replace the device. Moreover, the need to administer antibiotics periodically to patients is expensive and patients who suffer from repeated infections often become resistant to particular antibiotics.
As an alternative to antibiotic treatment and/or device removal, U.S. Pat. No. 5,263,930 proposes to provide a disinfectant reservoir in an implantable vascular access port. The reservoir includes a septum to permit periodic replenishment with a suitable anti-microbial agent. Agent introduced into the reservoir flows into an access lumen through the device. Catheters and other devices inserted into the access lumen become coated with the anti-microbial agent to provide a barrier against infection along the percutaneous access route. While potentially beneficial, the provision of a static volume of anti-microbial agent within a reservoir does not provide flushing and active decontamination of the tissue pocket surrounding the implanted port. Thus, should bacteria be introduced into the tissue pocket, it is unlikely that the anti-microbial agent would be effective to inhibit infection.
For these reasons, it would be desirable to provide improved methods and devices for inhibiting bacterial and other infections in subcutaneously implanted devices. It would be particularly desirable to provide methods and devices for active flushing of the implanted device as well as the tissue pockets and regions surrounding the device in order to maximize the disinfection process. It would be particularly useful if such methods and devices were applicable not only to implantable ports but also to other subcutaneously and transcutaneously implanted devices. At least some of these objectives will be met by the present invention as described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,263,930 has been described above. A transcutaneous vascular access port sold under the tradename HEMASITE.RTM. II by Renal Systems, Inc., Minneapolis, Minn., includes an above-skin reservoir for a bactericide, as described in a brochure entitled Vascular Access System copyrighted by the manufacturer in 1984. Catheters having bacteriocidal coatings and release capabilities are described in U.S. Pat. Nos. 5,599,321; 5,591,145; 5,482,740; 5,261,896; 5,236,422; 5,004,455; 4,959,054; 4,767,411; and 4,579,554.